The basic design of grain elevators has not changed substantially for many years. U.S. Pat. Nos. 281,214, W. Watson, July 10, 1883; 867,962, W. L. Finton, Oct. 15, 1907; 1,580,073, W. O. Nothnagel, April 6, 1926; and 3,931,877, L. L. Albaugh, Jan. 13, 1976, are representative of the prior art.
Canadian Pat. Nos. 1,120,281 and 1,126,467 issued to Buffalo Beton Ltd. provided substantial improvements to the art in disclosing construction of an elevator in pre-fabricated form.
The pre-fabricated grain elevator in Canadian Pat. No. 1,120,231 relates to a structure for storing granular material comprised of a plurality of parallel, vertically extending rows of inclined bins, each bin being discrete with respect to all adjacent bins. Each bin is charged at the upper end by means of a vertical passage in a precast concrete feed manifold for each vertical row of bins. Each bin is discharged at a normally closed lower end utilizing a similar fluted manifold.
The bins in U.S. Pat No. 1,120,231 are defined by modules in the form of preformed, reinforced concrete sections, which are readily interconnected on site for quick construction of an elevator. In the preferred form, the sections and consequently the bins are rectangular in cross-sectional configuration, with a bottom wall and integral side walls. When the sections are interconnected end-to-end they form an elongated sloping bin. A plurality of bins are stacked one on top of another to form a vertical row of bins, the top of each bin being closed by a superjacent bin, the tops of the uppermost bins being closed by a roof.
The granular material process, i.e., the movements of the grain to, through and from the elevator utilizes conventional material handling devices and machinery. Grain carried to the elevator in trucks is weighed and fed into receiving pits; bucket conveyors elevate the grain vertically; screw conveyors transport the grain laterally; and the precast concrete feed manifolds, complete with sliding plugs, controls charging and discharging operations from individual bins.
One of the objectives of the pre-fabricated grain elevator in Canadian Pat. No. 1,120,231 was to alleviate, at least partially, the hazard of fire and explosion propagation throughout the structure. This was accomplished by means of self-contained, entirely closed individual bins utilizing explosion relief in the form of end wall panels. Another objective of the elevator was the use of pre-formed structural components to alleviate the problem of maintaining a large work force and comprehensive fabrication control in remote areas where elevators are usually required. The prefabricated units are manufactured in a factory-controlled environment and shipped to a site for assembly. A third objective of the elevator was to alleviate the problem of overpressures on the bin walls during filling and emptying. These pressures are difficult to determine and costly to design for. There have been dramatic elevator failures resulting from the improper calculation of these overpressures.
The above-described pre-fabricated grain elevator and its sloping storage bin concept is a new improvement to the state of the art in elevator design and construction. However, the development of this art has not remained static. The present invention encompasses the important fundamental concepts of the aforementioned pre-fabricated grain elevator and it expands on these concepts to include new and unobvious improvements.
The improvements of the present invention relate to alleviating, at least partially, the problem of overpressure exerted on bin walls during filling and emptying of deep bins. The pre-fabricated grain elevator described in Canadian Pat. No. 1,120,231 partially alleviated this problem by sloping the bins at or near the angle of repose of the stored material, thereby creating a non-confined grain flow pattern, i.e. a grain flow pattern where the moving particles are on or near a free surface. However, the structure in Canadian Pat. No. 1,120,231 restricted the storage bin height and was therefore only workable with relatively shallow bins. The design of deep bins reverted back to the conventional vertical storage facilities with their aforementioned problems. The design of conventional deep bins ultimately requires an educated guess at the design overpressure values. One feature of the present invention is to eliminate the shallow bin constraint associated with the prior art and provide complete flexibility in storage bin depth and shape. The improvements according to the present invention remove the uncertainty in deep storage bin design by eliminating the phenomenon of overpressure in deep bins.